Field of the Invention
The present invention relates to a compound for forming an organic film for use in multilayer resist for fine processing to manufacture a semiconductor apparatus, etc., or an organic film for planarization to manufacture a semiconductor apparatus, etc. The invention also relates to a composition for forming an organic film containing the compound, a method for forming an organic film using the composition, and a patterning process using the composition.
Description of the Related Art
As LSI advances toward high integration and high processing speed, miniaturization of pattern size is progressing rapidly. Along with the miniaturization, lithography technology has achieved a fine patterning by shortening wavelength of a light source and selecting an appropriate resist composition accordingly. The composition mainly used is a positive photoresist composition for monolayer. The monolayer positive photoresist composition not only allows a resist resin to have a skeleton having etching resistance against dry etching with chlorine- or fluorine-based gas plasma, but also provides a resist mechanism that makes an exposed part soluble, thereby dissolving the exposed part to form a pattern and processing a substrate to be processed, on which the resist composition has been applied, by dry etching using the remaining resist pattern as an etching mask.
However, when the pattern becomes finer, that is, the pattern width is reduced without changing the thickness of the photoresist film to be used, resolution performance of the photoresist film is lowered. In addition, pattern development of the photoresist film with a developer excessively increases a so-called aspect ratio of the pattern, resulting in pattern collapse. Therefore, the photoresist film has been thinned along with the miniaturization of the pattern.
On the other hand, a substrate to be processed has been generally processed by dry etching using a pattern-formed photoresist film as an etching mask. In practice, however, there is no dry etching method capable of providing an absolute etching selectivity between the photoresist film and the substrate to be processed. The resist film is thus damaged and collapses during processing the substrate, and the resist pattern cannot be precisely transferred to the substrate to be processed. Accordingly, higher dry etching resistance has been required in a resist composition along with the miniaturization of the pattern. In the meantime, a resin used for the photoresist composition has been required to have low absorption at the exposure wavelength in order to enhance the resolution. The resin thus shifts to a novolak resin, polyhydroxystyrene, and a resin having an aliphatic polycyclic skeleton as the exposure light shifts from i-line to KrF and ArF, which have shorter wavelength. This shift actually accelerates an etching rate under dry etching condition for processing the substrate, and recent photoresist compositions having high resolution tend to have low etching resistance.
Thus, the substrate to be processed has to be dry etched with a thinner photoresist film having lower etching resistance. The need to provide a composition used in this process and the process itself has become urgent.
A multilayer resist method is one of solutions for these problems. This method is as follows: a middle layer film having a different etching selectivity from a photoresist film (i.e., a resist upper layer film) is placed between the resist upper layer film and a substrate to be processed; a pattern is formed in the resist upper layer film; the pattern is transferred to the middle layer film by dry etching using the resist upper layer film pattern as a dry etching mask; the pattern is further transferred to the substrate to be processed by dry etching using the middle layer film as a dry etching mask.
One of the multilayer resist methods is a three-layer resist method, which can be performed with a typical resist composition used in the monolayer resist method. For example, this three-layer resist method includes the following steps: an organic film containing a novolak resin or the like is formed as a resist underlayer film on a substrate to be processed; a silicon-containing film is formed thereon as a resist middle layer film; a usual organic photoresist film is formed thereon as a resist upper layer film. Since the organic resist upper layer film exhibits an excellent etching selectivity ratio relative to the silicon-containing resist middle layer film when dry etching is performed with fluorine-based gas plasma, the resist upper layer film pattern can be transferred to the silicon-containing resist middle layer film by dry etching with fluorine-based gas plasma. This method allows the pattern to be transferred to the silicon-containing film (resist middle layer film) even using a resist composition that is difficult to form a pattern having a sufficient film thickness for directly processing the substrate to be processed or a resist composition that has insufficient dry etching resistance for processing the substrate. Further, dry etching with oxygen gas plasma or hydrogen gas plasma allows the pattern to be transferred to the organic film (resist underlayer film) containing a novolak resin or the like, which has a sufficient dry etching resistance for processing the substrate. As to the resist underlayer film, many materials are already known as disclosed in Patent Document 1.
In recent years, on the other hand, there is a growing need for an underlayer film having excellent filling and planarizing properties as well as dry etching resistance. For example, when the substrate to be processed used as a base has a fine pattern structure such as hole and trench, the filling property is required to fill the gaps of the pattern without space. In addition, when the substrate to be processed used as a base has steps, or when one wafer contains both a pattern-dense region and a pattern-free region, the surface of the substrate or the wafer requires being planarized by the underlayer film. Planarizing the surface by the underlayer film reduces fluctuation in film thickness of a middle layer film and a resist upper layer film formed thereon, thus increasing a focus margin in lithography or a margin in a subsequent step of processing the substrate to be processed.
To improve the filling and planarizing properties of an underlayer film composition, addition of a liquid additive such as polyether polyol has been proposed (Patent Document 2). However, an organic film formed by this method contains many polyether polyol units, which are inferior in etching resistance. Thus, this film has a markedly lowered etching resistance and is unsuitable for the three-layer resist underlayer film. For this reason, there are demands for a resist underlayer film composition having both excellent filling and planarizing properties and sufficient etching resistance as well as a patterning process using this composition.
Moreover, the organic film composition excellent in filling and planarizing properties is not limited to materials of the underlayer film for multilayer resist. This composition is widely usable also as a planarizing material for manufacturing a semiconductor apparatus, e.g., for planarizing a substrate prior to patterning by nanoimprinting. For global planarizing in the semiconductor apparatus manufacturing process, a CMP process is now generally used. However, the CMP process is costly, so that this composition is also expected to be used for the global planarizing method, instead of CMP.